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Microbes living in extreme environments often adopt strategies for survival, however, only a few studies have examined the adaptive mechanism of deep-sea bacteria in in-situ environments. In this study, transcriptomic data of the deep-sea piezotolerant and psychrotolerant actinomycete Microbacterium sediminis YLB-01 under the conditions of NPNT (normal temperature and pressure: 28 °C, 0.1 MPa), HPNT (normal temperature and high pressure: 28 °C, 30 MPa), NPLT (low temperature and atmospheric pressure: 4 °C, 0.1 MPa) and HPLT (low temperature and high pressure: 4 °C, 30 MPa) were examined and compared. Transcriptome results showed that M. sediminis YLB-01 responds to deep-sea low temperature under high-pressure environments by upregulating the ABC transport system, DNA damage repair response, pentose phosphate pathway, amino acid metabolism and fatty acid metabolism, while down-regulating division, oxidative phosphorylation, the TCA cycle, pyruvate metabolism, ion transport and peptidoglycan biosynthesis. Seven key genes specifically expressed under HPLT conditions were screened, and these genes are present in many strains that are tolerant to low temperatures and high pressures. This study provides transcription level insights into the tolerance mechanisms of M. sediminis YLB-01 in a simulated deep-sea in situ environment. [ABSTRACT FROM AUTHOR]

A halophilic, Gram-staining-negative, rod-shaped, flagellated and motile bacterium, strain QX-1 T, was isolated from deep-sea sediment at a depth of 3332 m in the southwestern Indian Ocean. Strain QX-1 T growth was observed at 4–50 °C (optimum 37 °C), pH 5.0–11.0 (optimum pH 7.0), 3–25% NaCl (w/v; optimum 7%), and it did not grow without NaCl. A phylogenetic analysis based on the 16S rRNA gene placed strain QX-1 T in the genus Halomonas and most closely related to Halomonas sulfidaeris (97.9%), Halomonas zhaodongensis (97.8%), Halomonas songnenensis (97.6%), Halomonas hydrothermalis (97.4%), Halomonas subterranea (97.3%), Halomonas salicampi (97.1%), and Halomonas arcis (97.0%). DNA–DNA hybridization (< 26.5%) and average nucleotide identity values (< 83.5%) between strain QX-1 T and the related type strains meet the accepted criteria for a new species. The principal fatty acids (> 10%) of strain QX-1 T are C16:0 (25.5%), C17:0 cyclo (14.0%), C19:0 cyclo ω8c (18.7%), and summed feature 8 (C18:1ω7c and/or C18:1ω6c, 18.1%). The polar lipids of strain QX-1 T are mainly diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unidentified phospholipid, unidentified aminophospholipid, and five unidentified lipids. The main respiratory quinone is Q-9. The G + C content of its chromosomal DNA is 54.4 mol%. Its fatty acid profile, respiratory quinones, and G + C content also support the placement of QX-1 T in the genus Halomonas. These phylogenetic, phenotypic, and chemotaxonomic analyses indicate that QX-1 T is a novel species, for which the name Halomonas maris is proposed. The type strain is QX-1 T (= MCCC 1A17875T = KCTC 82198 T = NBRC 114670 T). [ABSTRACT FROM AUTHOR]

A Gram-staining-negative, aerobic, flagellated, motile, rod-shaped, halophilic bacterium QX-2T was isolated from the deep-sea sediment of the Southwest Indian Ocean at a depth of 2699 m. Growth of the QX-2T bacteria was observed at 4–50 °C (optimum 30 °C), pH 5.0–12.0 (optimum pH 6.0) and 0%–30% NaCl (w/v) [optimum 4% (w/v)]. 16S rRNA gene sequencing revealed that strain QX-2T has the closest relationship with Halomonas titanicae DSM 22872T (98.2%). Phylogeny analysis classified the strain QX-2T into the genus Halomonas. The average nucleotide identity and DNA–DNA hybridization values between strain QX-2T and related type strains were lower than the currently accepted new species definition standards. Principal fatty acids (> 10%) determined were C16:0 (12.41%), C12:0-3OH (25.15%), summed feature 3 (C16:1ω7c and/or C16:1ω6c, 11.55%) and summed feature 8 (C18:1ω7c and/or C18:1ω6c, 16.06%). Identified polar lipids in strain QX-2T were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unidentified phospholipid, unidentified aminophospholipid and five unidentified lipids (L1–L5). The main respiratory quinone was Q-9. The content of DNA G+C was determined to be 54.34 mol%. The results of phylogenetic analysis, phenotypic analysis and chemotaxonomic studies showed that strain QX-2T represents a novel species within the genus Halomonas, for which the name Halomonas sedimenti sp. nov. is proposed, with the type strain QX-2T (MCCC 1A17876T = KCTC 82199T). [ABSTRACT FROM AUTHOR]